Sizing a Virtual Server

Question

I would like to replace four aging physical servers with one virtual server. What is the best way to insure the VM server is sized correctly? The requirements of the apps that will be running on the four servers are

APPLICATION SERVERS - QTY 3 - These will run the application layer for the web server, Business Objects Business Intelligence app, and various other small client server apps. The three most heavy hitting apps each have the following server requirements. So, if I bought three physical servers, this would be the requirements for each of them Processor - Dual 2.83 GHZ (or faster) Ram - 4 GB Raid 5 - 50-100GB usable space NIC - 1 GB

Web Server - this will run one asp.net e-business app that will talk to our dedicated SQL server and the three app servers above. The E-Business software has these requirements for the web server

Processor - Quad 2.83 GHZ (or faster) Ram - 8 GB Raid 5 - 50-100GB usable space NIC - 1 GB

What is the best tool to determine what I need from a hardware standpoing in a virtual server? I am planning on using VMWare.

Answer 1

Monitor the performance of the servers you have now.

Memory and IOPS is the most important to think about. Cpu is rarely an issue.

If you got the money for it try and get a SAN that you can expand on later and 2 Physical servers. This way you can do hardware maintenance on the servers without going offline.

Answer 2

Vmware Capacity Planner is your best bet. However, you will have to sign up as a partner (easy to do), or have a partner/reseller run it for you. In the end, you will have accurate details about the utilization of your current hardware, as well as a good idea of what you will need.

Answer 3

Without more information about the average load placed on these servers it's going to be hard to give a great answer.

I can tell you that if the load is "average", you can probably get away with running all of these server's on a single ESXi box.

In our production enviornment we have ~45 VM's running accross 4 ESX boxes with no problems what so ever. We could run even more from a CPU usage standpoint. RAM is the first thing that we will run out of. However we are only consuming about 50% right now (each system has 32GB so we have 128GB total).

Answer 4

Instead of trying to size-up a BIG machine to do it, I'd recommend exploiting the fact that you have VMs and can spawn them as and when necessary. So, I'd recommend buying a bunch of smaller machines and distributing your work-load across them.